Summary: Signal peptide binding domain
Signal peptide binding domain Provide feedback
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Clemons WM Jr, Gowda K, Black SD, Zwieb C, Ramakrishnan V; , J Mol Biol 1999;292:697-705.: Crystal structure of the conserved subdomain of human protein SRP54M at 2.1 A resolution: evidence for the mechanism of signal peptide binding. PUBMED:10497032 EPMC:10497032
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This tab holds annotation information from the InterPro database.
InterPro entry IPR004125
The signal recognition particle (SRP) is a multimeric protein, which along with its conjugate receptor (SR), is involved in targeting secretory proteins to the rough endoplasmic reticulum (RER) membrane in eukaryotes, or to the plasma membrane in prokaryotes [PUBMED:17622352, PUBMED:16469117]. SRP recognises the signal sequence of the nascent polypeptide on the ribosome, retards its elongation, and docks the SRP-ribosome-polypeptide complex to the RER membrane via the SR receptor. Eukaryotic SRP consists of six polypeptides (SRP9, SRP14, SRP19, SRP54, SRP68 and SRP72) and a single 300 nucleotide 7S RNA molecule. The RNA component catalyses the interaction of SRP with its SR receptor [PUBMED:17507650]. In higher eukaryotes, the SRP complex consists of the Alu domain and the S domain linked by the SRP RNA. The Alu domain consists of a heterodimer of SRP9 and SRP14 bound to the 5' and 3' terminal sequences of SRP RNA. This domain is necessary for retarding the elongation of the nascent polypeptide chain, which gives SRP time to dock the ribosome-polypeptide complex to the RER membrane. In archaea, the SRP complex contains 7S RNA like its eukaryotic counterpart, yet only includes two of the six protein subunits found in the eukarytic complex: SRP19 and SRP54 [PUBMED:12364595].
This entry represents the M domain of the 54 kDa SRP54 component, a GTP-binding protein that interacts with the signal sequence when it emerges from the ribosome. SRP54 of the signal recognition particle has a three-domain structure: an N-terminal helical bundle domain, a GTPase domain, and the M-domain that binds the 7s RNA and also binds the signal sequence. The extreme C-terminal region is glycine-rich and lower in complexity and poorly conserved between species.
These proteins include Escherichia coli and Bacillus subtilis ffh protein (P48), which seems to be the prokaryotic counterpart of SRP54; signal recognition particle receptor alpha subunit (docking protein), an integral membrane GTP-binding protein which ensures, in conjunction with SRP, the correct targeting of nascent secretory proteins to the endoplasmic reticulum membrane; bacterial FtsY protein, which is believed to play a similar role to that of the docking protein in eukaryotes; the pilA protein from Neisseria gonorrhoeae, the homologue of ftsY; and bacterial flagellar biosynthesis protein flhF.
|Cellular component||signal recognition particle (GO:0048500)|
|Molecular function||7S RNA binding (GO:0008312)|
|Biological process||SRP-dependent cotranslational protein targeting to membrane (GO:0006614)|
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Curation and family details
|Seed source:||Structural domain|
|Number in seed:||124|
|Number in full:||4974|
|Average length of the domain:||100.10 aa|
|Average identity of full alignment:||43 %|
|Average coverage of the sequence by the domain:||21.33 %|
|HMM build commands:||
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 23193494 -E 1000 --cpu 4 HMM pfamseq
|Family (HMM) version:||14|
|Download:||download the raw HMM for this family|
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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the SRP_SPB domain has been found. There are 40 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein seqence.
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